This is the prayer to St. Michael the Archangel by Pope Leo XIII. I put it to my own melody a few years ago.
Saint Michael the Archangel,
defend us in battle.
Be our protection against the wickedness and snares of the devil.
May God rebuke him, we humbly pray;
and do Thou, O Prince of the Heavenly Host -
by the Divine Power of God -
cast into hell, satan and all the evil spirits,
who roam throughout the world seeking the ruin of souls.